Maintenance and Troubleshooting of Progressing …

1 Maintenance and Troubleshooting of Progressing Cavity Pumps Chad Huskey MOYNO Tech Eng. 4 The Progressing Cavity Pump and it s Geometry A Progressing cavity (PC) pump, or a single screw pump, is a positive displacement pump and therefore a fixed volume is displaced with each revolution of the pump s Rotor. The Rotor forms a single helix (like a corkscrew) and rotates eccentrically in the Stator. The Stator has a double helix cavity (like a double corkscrew) double the total volume of the rotor. When combined, as the rotor turns, cavities or pockets nearly half of the total volume are formed in the stator which push the product from the suction toward the discharge end of the pump. 5 Rotor Geometry Crest to crest (called Major) Circular cross-section (called Minor) Machined in a helical shape similar to a corkscrew 6 Stator Geometry Oval shaped cavity cross-section. Similar geometry as Rotor but uses a double helix.

2 Available in several elastomers, metal, or urethane construction materials. 7 Cavities As Rotor orbits (turns eccentrically) inside the Stator. The motion creates cavities and progresses them from suction to discharge. 8 End View of Rotor/Stator Combination LOOKING AT END VIEWS OF ROTOR TURNING IN STATOR, AS THE ROTOR COMPLETES ONE REVOLUTION. This feature results in a continuous, non-pulsating flow because the sum of any two opposing cavities is a constant. 90, 270 180 When the rotor is turned within the stator, the total cross-sectional area of the cavities remains the same regardless of the position of the rotor in the stator (see illustration below). 4e 4e 0 9 Application Variables APPLICATION INFLUENCES THE BIG THREE Abrasion Temperature Viscosity 10 Abrasive Characteristic Fluids Press/stage None Water, Polymer, Oil 87 PSI Light Milk or Lime 65 PSI Medium Sludge, Clay or Gypsum Slurries, Chocolate, Drilling Mud 43 PSI Heavy Emery Dust, Lapping Compounds, Grout, Sand, Granulated Sugar 20 PSI Effects of Abrasion Abrasive fluids = Wear Wear is proportional to speed; minimize speed to minimize wear.

3 De-rate pressure per stage to limit slip amount .. 87 PSI for no abrasion; 20 PSI for heavy abrasion. Specify oversize Rotor to increase interference fit = longer life. Use abrasion resistant Stator material or softer durometer elastomers: RM 100M, RM 103, Urethane etc. Double chrome rotor for additional Rotor base metal protection. 11 Effects of Temperature Stator Elastomers swell from 70 to 130 (physical Rotor dimensions require adjustment above this 130 temperature) and Elastomers shrink with Lower temperature (Below 50 ). Metal parts such as the rotor and drive train tend to expand and contract at a negligible rate than elastomer counterparts. Since Stator is bonded to a metal tube, the rubber can only swell inward on the rotor, or shrink away from the rotor. This changes the compressive fit between the rotor and stator. Again, to keep a standard fit, the Rotor requires under sizing above 130 , and over sizing below 50.

4 Under extreme heat or cold, elastomer Stators may not be appropriate. Metal Rotor and Stator combinations can be used for extreme temperature applications because they swell or shrink at the similar rates. 12 Cavity only half full The more viscous a fluid, the slower the pump will have to run in order to permit the fluid to flow into the cavity. 1 CPS = Above 1800 RPM 100 CPS = 700 RPM 1000 CPS = 150 RPM 10,000 CPS = 30 RPM Loss of Fill (volumetric) Efficiency starts at Even at reduced speeds, the pump may not develop 100% volumetric efficiency and this must be accounted for in the selection process. Effects of Viscosity 13 Material Viscosity (centipoise) Water @ 70deg F 1-5 Blood or Kerosene 10 Anti-freeze or Ethylene Glycol 15 Motor Oil SAE 10 or Corn oil 50-100 Motor Oil SAE 30 or Maple Syrup 150-200 Motor Oil SAE 40 or Castor Oil 250-500 Motor Oil SAE 60 or Glycerin 1-2 thousand Karo Corn Syrup or Honey 2-3 thousand Blackstrap Molasses 5-10 thousand Hershey Chocolate Syrup 10-25 thousand Ketchup or Common Mustard 50-70 thousand Tomato Paste or Peanut butter 150-250 thousand Crisco Shortening 1-2 million Caulking compound 5-10 million Window Putty (glazing compound) 100 million Effects of Viscosity 14 Summary The standard PC pump consists of a Rotor (metal) which rotates within an elastomeric Stator.

5 The Rotor has a circular cross-section and is machined in a single helix like a corkscrew. The Stator cavity is molded as a double helix with an Oval cross-section. The helix geometry is similar to the rotor to create an interference fit. As the rotor turns inside the stator it orbits on an eccentric (at an offset around the center axis), this motion creates cavities that progresses from suction to discharge; moving product and building pressure. How does a MOYNO Pump Work? 15 Summary The MOYNO design creates a low shear, metered, and pulse-less flow. The PC pump is able to effectively handle water-like to super viscous fluids including levels of air or gases. It can gently pump large particulates and handle abrasive solids. Provides excellent suction capabilities and does not air lock. The flexible geometry of the MOYNO pump allows. Multiple drive end choices (power) and multiple stages (pressure).

6 MOYNO pumps allow precise control of the interference fit. MOYNO can best match the pump to your application. Progressing Cavity Pump Advantages 16 General Maintenance PUMP Maintenance DAILY INSPECTION; Lip seals on bearing housing Packing/Mech seal (flow/pressure/noise) Gear reducer (temp/noise). WEEKLY MAINT; Adjust packing (should drip 2-5 times per minute) Lube packing (typically 2-3 pumps per week). Preventative Maintenance Most of the Maintenance needed for a MOYNO pump is based on look-feel YEARLY MAINT; Replace packing, inspect shaft wear. Replace automatic lubricator (if applicable). Pull spool piece to inspect pipe internal condition. Lubrication Schedule Bearings Bearings are lubricated and the factory and do not normally need periodic re-lubrication-recommended only when drive shaft is removed for Maintenance . Packing Once a week or more, frequency determined by process.

7 Gear Joints Only recommended when gear joints are disassembled. (example; when replace rotor) Lubrication Suppliers MOYNO Progressing CAVITY PUMPS USE TWO LUBRICANT FOR MOST INDUSTRIAL APPLICATIONS. (TEMPERATURES 400 F OR LESS) DuBOISE CHEMICAL ACG 2 , AND MOBIL-1 NLGI Grade 2 DuBOISE CHEMICAL. ACG 2 and MOBIL-1 NLGI Grade 2 ARE RECOMMENDED FOR: GEAR JOINTS PIN JOINTS BEARINGS INDUSTRIAL PACKINGS THE FOLLOWING LUBRICANTS ARE ACCEPTABLE FOR: PIN JOINTS BEARINGS INDUSTRIAL PACKINGS 1. ACG-2 DuBOISE CHEMICAL (FACTORY INSTALLED) 2. MOBIL 1 NLGI Grade 2 MOBIL CHEMICAL (RECOMMENDED) 3. MOBILUX EP2 MOBIL CHEMICAL 4. ALVANIA EP2 SHELL OIL 5. MYTILUS 2 SHELL OIL 6. SUNAPLEX 992 EP SUN OIL 7. ACL-2 FISKE BROTHERS 8. TRIBOL 823-2 CASTROL 9.

8 STARPLEX SERIES TEXACO FOR MOYNO SANITARY PUMPS, THE RECOMMENDED PACKING LUBRICATION IS FGG - 2 from DuBoise Chemical or Accrolube 2 from Accro-Seal or equivalent. NOTE: THE ABOVE LUBRICANTS ARE ALL NLGI Grade 2 Greases Manual Diagrams 21 FAILURE ANALYSIS AND EXAMPLES OF WORN & FAILED MOYNO PARTS Failure Analysis Failure Analysis Equipment failures are frustrating and inconvenient. Some of the more useful information you will gather as a Maintenance professional or operator will come from failure analysis. That doesn t mean that a failure is not useful. Failure Analysis Was the failure caused by operator error? Is there a process issue? Was there a mechanical shortfall? Failure analysis will help to determine future preventative Maintenance and narrow the decision making for necessary changes concerning process or equipment. Failure Analysis Inspecting Rotors Failure Analysis Inspecting Stators A worn stator may appear pitted and gauged, or may appear smooth similar to new.

9 Performance is the best measure of rotor to stator fit. If unable to measure performance adequately, suspected stator wear can be evaluated by a MOYNO sales representative. Failure Analysis What is cavitation and how can I tell if my pump is cavitating? In summary, cavitation is an abnormal condition that can result in loss of production, and equipment damage. In the context of pumps, the term cavitation implies a dynamic process of formation of bubbles inside the liquid, their growth and subsequent collapse as the liquid flows through the pump. It can be vaporous or gaseous. Both types of bubbles are formed at a point inside the pump where the local static pressure is less than the vapor pressure of the liquid (vaporous cavitation) or saturation pressure of the gas (gaseous cavitation, also referred to as air binding ). The noise and pump vibration is caused by the collapse of the air bubble when it gets pressurized.

10 Typically in a MOYNO pump the cause of cavitation is a lack of suction volume. The symptoms are reduced flow, a rumble with vibration or and may include a rapid popping sound. TYPICAL ROTOR ABRASIVE WEAR PATTERN NOTE THE TELLTALE RIDGES Failure Analysis ABRASIVE WEAR ON A ROTOR NOTE THE RIDGES OR GROOVES Failure Analysis ABRASIVE WEAR ON A 316ss ROTOR NOTE THE DEEP GAUGING GROOVES Failure Analysis TYPICAL ROTOR EVEN WEAR PATTERN A LITTLE TOO WORN TO RE-PLATE ADJUSTING THE Maintenance INTERVAL MAY LOWER COSTS Failure Analysis CHEMICAL ATTACK TO THE EXPOSED CARBON STEEL BASE METAL OF A CHROME PLATED ROTOR. A SYMPTOM INDICATING THE ROTOR BASE METAL IS NOT COMPATIBLE WITH THE PROCESS Failure Analysis CHEMICAL ATTACK UNDERMINING THE CARBON STEEL BASE METAL THRU THE CHROME PLATING. Failure Analysis CHEMICAL ATTACK TO THE CARBON STEEL BASE METAL THRU THE CHROME PLATING. Failure Analysis CHEMICAL ATTACK TO THE 316 SS BASE METAL UNDER THE CHROME PLATING.